const someAsyncThing = function () {
  return new Promise((resolve, reject) => {
    // 下面一行会报错, 因为x没有声明
    resolve(x + 2)
  })
}

someAsyncThing().then(() => {
  console.log('everything is great')
})


setTimeout(() => {
  console.log(123)
}, 2000)
